They are worried about Gabe's problems because if he keeps having them, he will not be able to get placed with a family. No family will want to put up with that. In that case, Gabe will just get released because he can't be placed with a family.
Jonas solves the problem by becoming something of a Giver himself. He starts to give Gabe some soothing memories to lull him to sleep. He knows that he is not really supposed to do that, but he can't help it -- he does not want Gabe to be released.
They are living in a perfect community, and if somebody gets it hard to attuned to the order, or just behave against the rules, they are simply excluded from the community, and this action is called “RELEASE”. They are worried about Gabe because if he keeps having his problems, he wouldn't get placed with a family unit, because he will be ‘incongurious’ and no family will want to put up with that. In that case, Gabe will just get released because he can't be placed with a family. Even though, that Jonas and his father doesn’t have such deep feelings like love, they still care about the baby and know that it would be so unfortunate to be realesed when you’re just a baby and had done nothing wrong.
(You can find how Jonas solve the problems at page 116-117, chap 14)